• Journal of the Institute of Electronics Engineers of Korea SP
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• v.42 no.2 s.302
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• pp.131-142
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• 2005

The low rate speech coders under 4 kbit/s are based on sinusoidal transform coding (STC) or multiband excitation (MBE). Since the harmonic coders are not efficient to reconstruct the transient segments of speech signals such as onsets, offsets, non-periodic signals, etc, the coders do not provide a natural speech quality. This paper proposes method of a efficient transient model :d a multi-mode low rate coder at 2.4 kbit/s that uses harmonic model for the voiced speech, stochastic model for the unvoiced speech and a model using aperiodic pulse location tracking (APPT) for the transient segments, respectively. The APPT utilizes the harmonic model. The proposed method uses different models depending on the characteristics of LPC residual signals. In addition, it can combine synthesized excitation in CELP coding at time domain with that in harmonic coding at frequency domain efficiently. The proposed coder shows a better speech quality than 2.4 kbit/s version of the mixed excitation linear prediction (MELP) coder that is a U.S. Federal Standard for speech coder.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.8
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• pp.737-742
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• 2015

Course correction munition are a weapson system for precision attacks and are assembled by applying a ballistic control system to existing projectiles. The roll control system is a subsystem of the ballistic control system and is placed between the guidance and control units inside of the projectile, which undergoes a 5000g lateral acceleration. Thus, it is very important to design the system to endure this load. Many developed countries evaluate the performance and safety of course correction munitions' parts using live-fire gun launch tests or a soft recovery system. However, these methods are expensive and slow. Thus, in this study, we develop impact analysis model of the roll control system using CAE. We apply the code to simulate impact phenomenon and use Johnson-Cook material model for modeling the high strain rate effect on the materials. We also design bearings in detail to analyze their behavior and verify the reliability of CAE model through gas-gun impact tests of the roll control system.

• Journal of the military operations research society of Korea
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• v.33 no.2
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• pp.101-113
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• 2007

The period of military personnel service will be phased down by 2014 according to 'The law of National Defense Reformation' issued by the Ministry of National Defense. For this reason, the ROK army provides discrimination education to 'newly recruited privates' for more effective individual performance in the on-the-job training. For the training to be more effective, it would be essential to predict the degree of achievements by new privates in the training. Thus, we used data mining techniques to develop a classification model which classifies the new privates into one of two achievements groups, so that different skills of education are applied to each group. The target variable for this model is a binary variable, whose value can be either 'a group of general control' or 'a group of special control'. We developed four pure classification models using Neural Network, Decision Tree, Support Vector Machine and Naive Bayesian. We also built four hybrid models, each of which combines k-means clustering algorithm with one of these four mining technique. Experimental results demonstrated that the highest performance model was the hybrid model of k-means and Neural Network. We expect that various military education programs could be supported by these classification models for better educational performance.

• Journal of Aerospace System Engineering
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• v.18 no.1
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• pp.11-20
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• 2024

In the recent era of NewSpace, unlike high-reliability satellites of the past, low-reliability satellites are being developed and mass-produced at a lower cost to launch constellations satellites. To achieve cost-effective cluster satellite development, satellite users and developers need to assess the feasibility of maintaining mission performance over the expected lifespan when cluster satellites are launched. Plans for replacements due to random failures should also be established to maintain performance. This study proposed a method for assessing system reliability and availability to maintain mission performance and establish replacement strategies for Earth observation constellation satellites. In this study, a constellation reliability and availability model considering mission performance required for a satellite constellation, situations of satellite backup, and additional ground backups was established. The reliability model was structured based on the concept of a k-out-of-n system and the availability model used a Markov chain model. Based on the proposed reliability model, the minimum number of satellites required to meet mission requirements was defined and satellites needed in orbit during the required mission period to satisfy mission reliability were calculated. This research also analyzed the number of spare satellites in orbit and on the ground required to meet the desired availability during required service period through availability analysis.

• Journal of Institute of Control, Robotics and Systems
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• v.9 no.11
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• pp.906-916
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• 2003

A multi-robot control algorithm using Petri-Net is proposed for 5vs5 robot soccer. The dynamic environment of robot soccer is modeled by defining the place and transition of each robot and converting it into Petri-Net diagram. Once all the places and transitions of robots are represented by the Petri-Net model, their actions can be chosen according to the roles of robots and position of the ball in soccer game, e.g., offensive, defensive and goalie robot. The proposed modeling method is implemented for soccer robot system. The efficiency and applicability of the proposed multiple-robot control algorithm using Petri-Net are demonstrated through 5vs5 Middle League SimuroSot soccer game.

• Journal of the Korea Institute of Military Science and Technology
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• v.17 no.6
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• pp.800-809
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• 2014

The gridded environmental data is usually provided by the numerical simulation coupled with a data assimilation technique and various inter- or extrapolation algorithms, both of which are based on the observation spanning from simple equipments to satellites. But it is difficult to represent the natural phenomenon such as sea mount, internal-wave, warm eddy in modeling or observation because of increase in the complexity of model. This paper introduces the algorithm artificially representing the natural phenomenon and the techniques applying it to the gridded volume data and smoothing for natural effects. Moreover, the inserted results are analyzed by use of graphical tool. The results can be used for the battle simulation or acoustic model.

• Journal of the Korean Data and Information Science Society
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• v.26 no.4
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• pp.985-995
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• 2015

Add-on selling can provide new chances to increase sellers' profits and meet customers' needs. Although prior studies have advocated add-on selling for its business value, there is an argument that add-on selling can cause customer repulsion. Therefore, we need to understand customer purchasing pattern related to add-on selling in order to promote it and to mitigate the customer repulsion. To that end, we applied data mining techniques to the 24,925 transactions of data from an online open market in Korea. We then conducted feature selection to investigate the most influential factors that can explain the characteristics of add-on selling transactions using a classification model. We also identified association rules among add-on selling and promotions. Finally, based on the findings in our experiments, we proposed add-on selling strategies for the target online market.

• Korean Management Science Review
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• v.27 no.1
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• pp.75-90
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• 2010

In this paper, we proposed new solution procedure of the air defense missile allocation problem. In order to find the optimal location of missile, we formulated a simple mathematical model maximizing the kill probability of enemy air threat including aircraft and missile. To find the Kill probability, we developed a new procedure using actual experimental data in the mathematical model. Actual experimental data mean real characteristic factor, which was acquired when the missile had been developed through missile fire experiment. The result of this study can offer practical solution for missile allocation and the methodology in this study can be used to the decision making for the optimal military facility allocation.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.05a
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• pp.196-200
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• 2005

Piezoelectric underwater acoustic transducer is a kind of device for underwater detection working as not only an actuator but also a sensor. The technique that can predict acoustical characteristics of transducer is important for robust design of transducer in harsh underwater environment. This paper represents the dynamic analysis of piezoelectric acoustic transducers based on finite element method through USAP software. Two dimensional model of Tonpilz transducer and three dimensional model of Flextensional transducer are generated for the dynamic analysis and some results obtained by USAP are compared with those by ANSYS.

• Journal of Korean Society for Quality Management
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• v.46 no.3
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• pp.397-410
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• 2018

Purpose: A main aims to classify quality attributes for quality assurance activities of military supplies by company size, and to derive the necessity for business improvement by company size to improve customer satisfaction through customer satisfaction coeffiecient and PCSI Index. Methods: Through a survey of defense and general businesses located in Busan and South Gyeongsang Province, the quality of service elements are classified and the client satisfaction factor and PCSI is calculated for the quality assurance activities. Results: Determine the current level of customer satisfaction with the quality of the Defence quality assurance service and present operational factors that need improvement by size of the company. Conclusion: The attractive quality of service factors for quality assurance work were in common and different and the need for improvement was identified based on differences in PCSI Index by Company size.